Since crude oil around the world is in short supply, the abundant heavy oil and super heavy oil increasingly attracted much attention. In the process of crude oil production, the crude oil in an oil layer penetrates into the well bottom through a porous media and then is lifted up to the ground by a lifting system. In the process of the heavy oil and the super heavy oil penetrating from the oil layer into the well bottom, some colloid, asphaltene, paraffin and other heavy components contained in the heavy oil and the super heavy oil are easily adhered to and accumulated on the surface near the wellhole due to their high content, high viscosity and slow flow velocity, which reduces the well yield, and the lifting process in the wellbore has high resistance and lifting difficulty, which brings great difficulty. Reducing the viscosity of the heavy oil and the super heavy oil and improving the flowability of the heavy oil and the super heavy oil are critical to solving mining, gathering and transportation issues of the heavy oil and the super heavy oil.
The viscosity reduction process commonly used in production of the heavy oil and the super heavy oil has reducing viscosity by heating, reducing viscosity by light oil blending and chemically reducing viscosity. Reducing viscosity by emulsifying the heavy oil and the super heavy oil exhibits significant advantage due to its low cost and high viscosity reduction rate and is widely applied.
Numerous examples of applying a heavy oil emulsifying viscosity depressant at home and abroad are the following: U.S. Pat. No. 4,333,488 reports a process for emulsifying heavy oil with an ethylene oxide-propylene oxide copolymer, which has a viscosity reduction rate of 80% for loco heavy oil with a viscosity of 340 cp at 21° C., wherein the appropriate mineralized water has a total ion concentration of 12,000 mg/L (in which the concentration of calcium and magnesium ions is 730 mg/L). CN1414058A discloses a viscosity reduction paraffin inhibitor for an oilfield polymer flooding well, which reduces the viscosity through chain scission caused by polymer oxidation.
CN88105018A discloses a process for reducing viscosity by emulsifying heavy oil, which emulsifies the heavy oil with polyxyethylated alkylphenol.
The above-mentioned prior art has the following disadvantages: 1) the employed heavy oil viscosity depressant is viscosity depressant with single performance, which has wide application range and is generally applied only to low viscosity heavy oil; 2) the high temperature resistant performance is poor and requirements for heavy oil quality is high; 3) the viscosity depressant has large dosage when in use and high cost; and 4) the viscosity depressant has a mineral salt resistance less than 3,000 mg/L and cannot be used when the calcium and magnesium ions in the formation water has high concentration.